Automatic telephone system.



T. G. MARTIN.

AUTOMATIC TELEPHONE SYSTEM.

'APPucmon FILED oc?. 21. |911.

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i Arme/umn man ocT.21. 19u. 1,236,859.

' Patented Aug. 14, 1917.

R.. fm@ 2. n mgm m .O in www@ @Q www T. G. MARTIN.

UTOMTIGELEPHONE SYSTEM. APPLlcATloN man oc. 21. 19H.

11,236,859 Patented Aug. 14,1917.

3 SHEETS-SHEET 3.

TTOR/VEYQ,

. ei'f..

'fht 1,.'1" a" citizenfo he United Statesl of 'Amer-ica,

.. resident; of Chicago, Cook county, Illinois, haveinvel` teda 'certainnew and useful Improvement in. Automatic vTelephoneA Sysl mSUf'r'Whi-chthe fQllOWing. is, a Specificaphone .'sysip'ems,-` and is particularlyry adapted for an automatic' system `in l`fwh1ch a YM"f lishin a.:jconnect1onfbetween a calling and jagcal ed'gsubscriber.. These switches are and'. are so arranged that the first scribersflin; *Each subscribers line is provided'- .'with"an individual or line switch' bymeans offwhich they may obtain access toone 'of thseiirst selectors. Certain of these line switches `and first selectors I have connection to the main exchange, while.other .so lishing such a connection, but can-merelyv i f communicate with other subscribers of their.

i i own private.. branch exchange.v

.. lFurther new features consist in the spel# eiiiq'construction-of,the selector switch by" means of 'which a more perfect and reliable byth rotary .'magnet ywhen the vletter is energized. The

f L l, fxUTomTIc.-Tnnnrnoirn SYSTEM.

pacification-of Letters v1I?atent. A. fait Epuration meaoetoberiziisil'.' semina G.' MARTN,

Myx,inventionfre-lates automatic `telev sericsof "switches are employed in'estab- ?.prefel'blyf'of the ordinary verticaland roi tary "typer,

" selectors! fire4 common to a plurality of sub-vl of the subscribers are prevented from estab-l .A` further novel feature consists intransf vmitting a signal to a calling subscnber'fwhen connection @from y operation is obtained. `'Ihe'selector switches employed are of the. type in which a rotary` 'magnet isleinployed `for. automatically rotat f -ing `the contact varmspver the trunks of-any.

.level -,un'til.anl idle tr1 1nkis.t'ouud.` 'A relay i is leniployedffon automatically iuterruptmg hi t vexchange tothecalled substation. The se- 'fPAEENT oFF-ICE.

'the circuit o'thisinterrupter relay soon as the rotary magnet energized. It"".wa's' `found, however', thatsometimes this yinterrupter relay voperated quicker, thanl the` private magnet and broke. the energizing circuit ofthe rotary magnet and allowed it to fall back and break the circuit of the `private magnet before the private v magnet hady become completely energized, and .therefore the `side switch was not tripped to third position.

Thelrotary'rnagnet would, therefore, aga-in be energized so as torotate the contact arms past the first trunkeven though this jtrunk were idle. By my improved arrangement this is rendered impossible by the addition of' springs o n the'private magnet, which sprlngs are'lncluded inthe circuitof the lnterrupter` relay. lIt vwill therefore be seen that this relaycannot be .energized t break the circuit ofthe rotary magnet until'after the private magnet has become completely r'energized so as vto close these springs. -This insures that the contact arms ofthe selector will always' stop on the first trunk provided this trunk is idle.v

` M These and other objects "of my invention .willwbe' more readily understood by reference to the. accompanying drawings, in whichi Figures'1, 2 and 3 Showa' on1pletecon nection between a kcalling substation A (Fig. 1) anda called substationA (Fig. 3i in'fa system embodying the principles of my invention. The substation A andftheapparatus 'shown in,`1`ig.` '1 are assumed to be located in a small private branch exchange,` while the apparatus shownin Figs. Qand is 'assumed tobelong vto the .main exchange. The connection shown 4is extended through 'thesubscribersf individua-l switch C and the selector".` switch .E iat the branchV exchange.

and through therepeater F, whichis included in atrunk line lead-ingto the main E and E2v andthe connectofHinjthe main ectoi-E nl 'the branch exchange, besides essltoxtrunk lines'l exchange, "from whence Vvthe connection exi i tends through" the first andsecond selectors `the diga called.

type. As shownY 'in Fig. 1, the substation A comprises the usual receiver 2, transmitter- :3,

hook 4, ringer 5 and condenser 6. Since it is an automatic substation it is also provided with v the well-known automatic calling device comprising a palr of impulse springs 7 'and 8 and a toothed impulse wheel 9, which. latter is controlled by the subi scriber through` thelmedium of a dial (not.

shown) provided withnger holes. The mechanism Vis so arranged that as the dial and impulse wheel are rotated forward by the subscriber, the im ulse springs are not operated, but. as the d1al returns to normal position said springs lare separated ,momentarily a lnumber offtimes, corresponding to The line switch C master switch D are nof the general type of line andmaster -switches disclosed inl British patent to` R. W.

James, No. 26,301 of 1906, but of the particular formshownin kBritish patent to T.

G. Martin, No. 1419 of 1910.' As herein rep-V resented, the liney switch C comprises, among other details, aplunger (not shown) which l is "attached" tothe end ofthe so-called plunger'I arm 10that is lcontrolled by the plural wofund.magnet 11.y Besides controlling the plungervarmvlO, the magnet ,11' also controls the relay'armatures 12 and 13 andcomprises lfour' windings, namely, a pull-in winding 14, a holding and cut-oif winding 1 5, a line winding y16 and an'fauxiliary'winding 17 The lateralyprojection vnear ythe ,center of the pivoted, provldes-the magnet.'with'twosep-v core ofthe magnet, means of which pro iecton Said lunar-inetA ,iS meuntd 11150114 the bracket 18 uponv which the armatures are arate magnetic circuits, so that the windings upon one end ofthe core do not affect the armatures. onthe other end. Of the two -windings upon theupper end ofthe magnet,

" only the wlnding 14 fis strongenoughto atv tract the plunger arm 10 from its normal position. Althoughthefhwinding -15 is not...

strong enoughl to` operate thearm` 10, it is I strongenough to holdit in its operated position' after ithas once been operated. When the plunger ar'm1'0 is attracted by themagnet :11,the'vplunge`r ofthe switch is`r forced into a group ofcontact springs 19, 20, 21', 22, 23, 24',

25 and 26,-forcing them into contact in pairs.

`Although :onlyione setpof springs 19-26 is y I, g shown, each switch' is provided witha plurality Lof vsuch sets of'springs, each' set vform'- inga terminal ofaseparate vtrunk 'line leadv ing 'to' a selector E. Each truiikvligneis mul- I ledthroughl 'the correspondingv contacts fo lallofy the switchesofxa group which is controlled by the master. switch D, while the rline,conductors ofthe substationMA are connected inmultipleJ to; the Isprings 19V and-21 ofv all of the'dierent lsets of'its switch The plungersof all the line switches ofthe group which is controlled by the master switch DA engage a socalled plunger shaft (not shown), and through the'medium of said master switch said plungers yare normally maintained opposite the terminal of an idle trunk line. The master switch con-v sists essentially of a motor,magne t 27 for rotating the ratchet wheel 28. The ratchet wheel 28 is connected with the plunger shaft in such a manner that a rotary motion of the ratchet wheel gives to the plunger shaft an oscillatory motion to carry the idle plunger's back and forth in front of their trunk terminal's. To the plunger shaft there is se'- cured a locking plate ,29",` rovided at its outer edge with a o, kopenings which are adapted to be engaged by a pin 30 on the end of the armature 31 of the 'relay 32. The

openings in the'plate 29 are spacedthat the pin can" 'engage one ef them and allow the armature 31 to assu'liije itsl normal position only when the plungers that fare in engagement with the plungerMsli-aft fare directly opposite the terminals bf a trunk line.

The-master switch is also pi'ovided with a. bank of contactsmcopiprising'a coniniinrsegment 33 and 'oneuiridividual 'contact a, for each trunk line to 'which the line switches have access. The wiper 34"is adapted to fmaintain the common segment 33 in electrical connection with the individual chtact of the trunk line before which the idle plungers are being held by the master switch.

The selector E is'of the general type disclosed in United States Letters Patent No. 815,321, granted March 13,="1906, to Keith, Erickson i and Erickson, 'being somewhat modified, however, in order. to operate in a twofwire system-that is, a system in which the central office apparatus is controlled by 'the calling subscriber over the two sides of ,the line 1n series. As herein represented, the

43. In this vinstance the release magnet isv p adaptedtoi restore the switch to normalposition immediately upon energizing, as shown in'United IStates Letters Patent No. 815,176,

grantedMa'rchf 13, to Keith, Erickson j and forconnector switches, rather ythan byk denergizing as 'shown in the selector patenthereinabove referred to. Thesprings 44, are' separated by the switch shaft when'- ever it is in its'lowest position. The-doublewound line relay 45 is normally connectedfamosas d .the sprin'gsof vSWitohff L61;I whereby-ifa circuitistcoinpleted.through, lys'47vand-48 are-slowl- 'thel-{iline winding16cof;the'linei'fswitch., C. PW; to 'lenergizeafter'llllhis'circuit?tendsfroin'ground G 'through icuitsj'hate `been brokem *tithe springs' -.1 62`Sar`1'dfy 63,vy 4lineconductor :68, giln'ay-Lbe accomplished by f- ;Springs,60'and l61,-iim1tn1-lse spif'ingszB- l.and 7, 70'

v c copper aro'undfone end Y receiver -2`,`" 'transmitter "3, fline conductor 169, inagnetf- "fllyA1 ,-fth'eselector:` ifi-) springs iiand- 64CLanduwindingal6i toit-the gfcta'ry magnet 39 'controls battery lead-.70,*thence to the battery B and gn P1142 electrically through to ground G.' The Winding 16, upon enercontact 89, rather than gizing,attracts the-armature 13, which o 75 wn in the said selector v-`crates to completea circuit from ground c uption of the rotary f through the springs 62 and 67 ,pull-inwindause theautomatc selec-f ing 14,` auxiliary winding 17, contact point is obtained through ythe 71 and the armatureV 31 to the battery lead 'irtlividual interruptor re- 70. The Winding `14, upon'. energizing, at- 80 tracts the plunger arm 10 and/the armature comprises a combination 12. The-armature12operatesto disconnect a for the purpose of re- -the line-winding and ground G from the @om the calling-substation line, While the `plunger arm 10 causes the epe theiii over the trunk conduc plunger. to force the springs19-26 into con 85 5 itle selector'E in the main tact as shown; The engagement of the M v l springs 19 and 21 with the springsj20 and a l ec y Vand E2 are essentially the 22, respectively, extends the llne conductors m sttlievsel tdi' E (Fig. 1 69 and 68 tothe selector E, whereupon its' 1in cti ofthe general type of Iline relay 45 becomes energlzed overa cir- 90 chidisclosed in said `United cuit extendingy fromground G2 through the p Pal-*tient No8-15,1176 abojg re- ""lower winding of the relay 45, springs 73 bei gmbdified slightly,fho wever, and :74, springs ,22k and 21, line68, thence 'i d two-wiressystem .in the throughvthe substation A and back over the -rr1n liBritish' patent to"\rT. Gj.jf.11linef16,9g springs ..19 and 20, springs 75 and 95 "1419oif51910.1` Like 'the-fselectorsy 76,1 andi/the upper windingof the relay 45 to isfgpifovided Withfashaft (notiv thebattery lead 70. The relay 45, 11POI1enri'ying;the wipers 51,*'52 ,and 53' v"ergizing, closes a circuit through the relay by the vertical and rotary 47. v'The relay 47, uponenergizing, extends The usual sidemswitch a circuit fromgroundGr2 through the springs 100 private magnet56y in the,y `77,l line switch bank springs 24 `and23and I I2 Vtrl-,57 there is shownra ringthe windng 15 0f thwith C150 the battery a y which i *providedfor they purpose lead. This energization of the Winding 15y is thelringing current generator for the purpose of maintaining the armature `lled lin soas to lsignal the called l2v and plunger ,ar i n 10 in theirroperated 105- ''Ihe tflking circuit through the positions after the circuit of the winding 14 v onnectoris ydivided into two sections indue. is broken by-the fal\ling back of the armaive/ ly1c onr'letzteldftiy'r thefcondensers 58 and 59. ture 13 when thefline winding `16 is "discon- Thef'substatin "Aand-the lineswitch' C vnectedfrom the lue. Therauxilia'ry Winding 45 rejsilnilarg'to' the substation A and' line 17 which isenergiged in 4series with the pull- 110 switch @respectively kAt L there is shown in winding 14, is,A short-circuited-When the ringing"currentf'generator,'- Foroperating plunger arm reaches its operated position centralbiiicefapparatus and4 for furnishand is therefore energized .only momentarily.

""urret, there are shown inthe This ymomentaryv energization, however," in- "luralityof batteries Bhaving fsures that the .armature 13 does not'breakv 115 nef'tei'in algruiided. If desired, only one thecircuit ofthe winding 14 `before the att'r'yn y d'b'iislcd, but preferably'one bat- 'winding 15 hashad time to be energized. r inieac rychange.L At M and M..tl1ere `The energization ofthe relay 47 of' the-sew tuobus'y signaling machines come., `lectorV also extends a guarding potential from sing'anintei'rupter and an vinduction coil. -ground Gr2v jhrough the springs 77,24 and `120 Having given affgeneral description-,ofthe 23; and -thewconductor 7 8` tothe yconnector 'pparatus' `Will'jirow be explainedin detail priratebank contacts of the callin line. ow thebrancheitchange substation A may' The closure of the springs-25 an -26 upon `thetoperation ofy ,the line s vg'itch- `completes a springs, contact point 79 (which fit is assumed corresponds to the trunkl line leading.

to thefselector E), wiper 34 (which is Vvat @thattitne restin othecontact 79) and the'.

relay-80 to the attery, lead 70. A, VThe relayin circuiti from ground G through" said 1.25'

80 and 32 would have remained energized by the switch C is idle, the relays 80 and 32 will denergize as soon as the plunger shaft; has -been rotated far enough -to carry the wiper 34 off the contact 79, but the armature 3.1. `will still remain held upby ,the plate 29 until the next opening therein comes directly underthe pin. 30, whereupon the armature 31 will drop back, vbreaking the eircuit of the-motor magnet' and allowing the plungersto come to rest infront -of this next trunk` line, with the wiper 34 resting upon the corresponding contact in the. master switch bank, as shown in the drawings. If

this next trunk had been busy, the wiper 34 would have found the corresponding contact grounded-and; consequently, the relays while-the next opening was passing'under the pin 30, -and the` plungers would haver been carried past the busy trunk toan idle 'y one.- n It 4will be seen that while the armature 331 is in its operated position, and consequently while the master switch is operating, the armature 31y is separated fromthe contact point 71, thereby disconnecting the battery from the pull-inwinding 14 of all the line switches operated by 'said master switchjlis making it limpossible to operate aline switch while the plunger is being moved.

The foregoing operations take place immediately upon the removal of the receiver at jthe calling substation and before the calling .45

device is operated for any of the digits o the called number. As has been previously planation,

explained, the selector E lhas access to connector switches in its own exchange and also to trunk lines leading to selector switches in' the main exchange. For the purpose of exit will be assumed that the second level of contacts of the 'selectors E in the branch exchange are connectedl with trunk lines leading to rst selectors E in the main exchange, while one or more of the remaining levels of contacts of theselectors E are connected -with connector switchesl which have access directly totheofsubstation lines of the branch exchange. vThus it will be seen that any branch exchange subscriber. may call any 'subscriber in his own-exchange by callingthree digits..rulliv order to call any= subscriber of the main exchange, the branch `ex-j l change subscribers mustrst call the d1git2,

to obtain connection with the trunk line leading to afirst selector inthe main exchange, after which any subscriber in the main exchange may-be called in the usual manner.

' Thus, in order for the subscriber at the branch exchange substation A to vcall the substation A', #2220, it will be necessary for the calling device at the substation A to be operated for the number 2-2220. When the calling device is operated for the first digit 2, the springsv 7 and 8 are momentarily separated twice, each time breaking the circuit ofv the selector line relay 45. The relay 47, being slow acting, does not have time to deenergize during the interruption of its cir- ,.cuit by the momentary denergization of the relay 45. Therefore, each time the relay 45 denergizes, a circuit is'closed from ground G5 through the spring 85 and its back contact, spring 86 and its front contact, relay 48, vertical magnet 38 and the side switch wiper 41 to the battery lead 70. The digit vcalled being 2, the verticall magnet receives two impulses over this circuit and operates to raise the switch wipers two steps to a position opposite the second level of bank contacts. The relay 48, which is energized in series with thevertical magnet, operates to close the circuit of the lowerwinding of the private magnet 42 as soon as the rst impulse is delivered to thevertical magnet, but, being a slow acting relay, said relay 48 does not denergize to break the circuit of the private *magnet until after the last impulse is delivered. When its circuit is broken the private magnet denergizes and permits the side switchto pass from first to second position. In second position, the side switch wiper 41 closes the circuit of the rotary magnet 49, said circuit extending from ground Gr2 through thev springs 77 of the relay 47, springs 87of the interrupter'relay 8,8, rotary magnet 3Q and the side switch wiper 41 to the battery lead. The rotary-1 magnet, upon energizing,l rotates the wipers one step onto the contacts of the first trunk of the second level and closes the circuit of the upper winding of the lprivate ,magnet The private magnet 42, upon energizing, -operates in conjunction with the rotary magnet to complete a circuit extending from ground Gr through the contact 89, private magnet springs 90 and the interrupter relay-jf88 to the battery lead. l,The interrupterk relay, upon energizing separates the-springs 87, thereby interrupting the circuit of the rotary magnet, which intu'rn denergizes and breaks the circuit offthe upper winding of the private magnet alf/the first trunkline is idle, the private magnet denergizes when the c ircuit` of `its upper winding is broken and permits the, side switch to lpass 0 `third position. If'thisfirst trunkv line is Sy its private bank contact' grounded and aholding circuit isi closed 4throughsaid wlpe'r,A

however, the private`- wiper 37 nds' private wiper 40 and the lowerwinding'of theprivate ma the case, the slde switch remains locked in second position and the denergization of the rotary magnet simply breaks the circuit of the interrupter 'relay 88. The interruptor operates to advance the wipers a second step.

The rotary magnet continues to advance the' wipers step by step in this manner until an idle trunk is reached, whereupon the private magnet. denergizes and permits the side switch to pass to third position.V It will be seen that the circuitof the interrupter relay 88 includes the springs 90 ,on -the private magnet, and lit is,' therefore, Yimpossible for the interruptor relay tointerrupt4 the rotary magnet circuit and permit it -to fall baci:`

before the private magnet has had time to become completely energized. This is to make sure that the side switch shall be stepped to third position when v`the wipers fare rotatedy the'- rst step in case the yfirst trunk line is idle. When the sideswitch passes to third position, whether after one andl side `switch wiper 41 tobattery. The

relayx4`6, upon energizing, disconnects the line relay v45 fromthe line andext'ends' the line lconnection over the heavy conductors through the wipers |35 and l36 to the line :relay 91 of the repeaterlF. The relay 91v thereupon energizes and closes a circuit from ground G7 through the springs 92 and 93 andthe relay 194 to the battery lead 70. The

f relay' 94, upon energizing, completes a circult from groundGSthrough the spri'ngs 95,

relay 9 6, selector private wiper ..37, sidey "switchwiper 40, whence the c1rcu1t divides into two branches, one branch passing through the relay 46 and the side swltch wiper 41 to the batteryv lead, while the other branch passes through the holding winding `150i the lineswitch C to battery. The closure of this circuit serves to maintain the relay'46 and winding 15 energized after the denergization of the relay 47,"which occurs soon after the vline relay45 of the lselector is disconnected from the line and allowed to break the circuit ofthe relay/17. The relay 96 of the repeater which was included in the above,circuit,'upoi1 energizing, operates to` close the normally open contacts in thetrunk circuitso. as to f'complete the connectionA be- .tween the calling line and the selector E',

(Figf 2);-` From the wiper 35 of the selector E the 'upper side of the linev connectiom'extends through the springs 97 .and'98 andthe V springs99 to. the trunk`conductori149:.jniThe other side ofthe line lyextends 'rlmlthe .se-

gnet42 to battery. This being` main exchange' is dependntmwprin #1th ene gization of the relay relay 88, upon denergizing, again 'closes 1h the circuit of the rotarymagnet, which then 1 '15' -ofl the line switch .lthencallingi'iline resistance in series 'v ciently to permit it to be ated. f The relay 96 is at i is so adjusted that when 1 circuit'with the winding 15 which) .is energized only stronggerreugh t cam th but' not strong venough to sepay tothe main exchange, abecause he' the trunk line at the repeater nifies to the calling subsicibenfth 'change subscribers and.ithemrnainzglclfiangew which are not lto be lpeg-mitte -main exchange are not pr i the' relay 107, springs springs .99, conductor Ufff;

.thus beseen that the comiectio lng substation with theuti'rst' As shown in the drawings;thentrindiiigtlfgo the line switch C is shuntedthy aiesistali 103. .Thisis for the purposeoi reducing withiethe melaiyf.. .fi

II shuntedby the resistance gfi'saidrela 9.

spring 104 into contact'withgithetspigigigi Q5 i? :e thesprin s'99i111dlQ2 -f -nsubscribe whose line switch is notfipiovide resistance -103 will not beiableftcall,

and 106l and close the spa unable tov close the contactsf'fl99 n f1.' I

subscriber attempts to cha-nge, he will not 4only a complete connection, but ,w be g1 busy signal in the following-aman@ paitial energization off'fathe `rel v. pletes a connection fromt'hebusy. ignaling machine Ml through theisprings A.f5-1044 0' and 106,"springs 101 andilQ@ 'selector el 36, thence to andl throughtthe; substation neigt@ back over .the other sidegofthe line.; the upper winding of theslinerela A g repeater to the battery lead 1 ,l 4ence 1051". tothe other terminal ofiithc busy., ignalin machine. This busy signalingacur attemptedto make a connection.,v rchyi possible. It will thus berseen tha 96 in the repeater. F servesrla which the service between th gbranchwexmaybe discriminating. Mills' thefsbstagt n which are to'be permitted@ Lea-,lb the exchange are rovided wit .a shunt-"ar the holding winding 15 ottheir While the line switchesfQz.

a shunt. A When therconnection ,extnde tothe selector E by thegrela 6 otmtlie .peater F, theline relay v107i), heise 1s lenergized over a circlt ci; ed' ground Gr18 through thea-,lewe

conductor 50, springs 1, the .repeater line relay,

and 11a and thefupper windingf the relay 107 to thebatterylead 1 15. When the substation calling device is operated for the second' digit 2, the. line relay 91 of the re peater F is denergized twice. momentarily.. Each time the relay 91 denergizes, 1t sepa-l rates the springs 110, thereby. breaking the circuit of-'the line relay 107 of the selector ner as has been explained for the selector- E. The operations of the selector E are effective to extend the-connection toA a. second selectorE2. At the'repeater F it will be seen that each time the relay 91 deenergizes in response to impulses from'thesubstation, it closes a circuit from ground Gr7 throughcthe spring' 92 and its back contact, springs. 116 of .the slow acting relay 94 and through the slow acting relay 117 to the battery lead 70. The relay 117 is energized by the first 'impulse and, being a slow acting'vv relay, does not denergize until after the last impulse is delivered. There` fore," while the repeater is operating to repeat the impulses over the trunk line 49-50,

the end of the trunk toward the calling line is disconnected at the contacts 100 and 101.4

and 97 and 98, andthe impedance .coil l.1-11 is short-circuited through the .springs 98 f and `118 so that it will not.. interfere with the operation .of the line relays of the' switches in the 'main exchange;vl When the substation calling device is operated yfor the third digit 2, the repeater F operates to repeatthe two impulses to the line relay 119 of the second selector E2 in the main exchange. The second selector E2 operates in the same manner as explained for the selector|-E to extend the connection over the trunk conductors 120 and 121 to an idle connector H ywhich is one of a group of connectors having Iaccess to the desired line #2220. When the connection is extended to the connector H, -its line relay 123 is energized as a consequence of a closed bridge across the line at the repeater F, in the saine manner as explained for the line relay 107 Vof the selector E. The relay l123, upon energizing, closes the circuit of the slow acting relay 124, which relay corresponds to v 4the relay 47 of the selector E. The relay 124, upon energizing, completes a holding circuit for the switching relays 125 and 126 of the selectors E2 and E. This circuit exitends from ground Gr9 through the springs 127,- conductor 122, private wiper 128, side 'switch wiper 129 to the point 130, thence 'branch passes through the wiper 133 of the selector E, side switch wiper 134, relay 126 y and the side switch wiper 135 to the battery Y lead 115. It will be seen that in the circuit just-traced a connection is extended from ground Gr9 to the selector private bank .con-

tacts-of. the trunks engaged by the ,selectorsy ,E and. E2, which coniiectionv 1" Jvi iesl a' guarding potential to prevent any other se?- lectors l'from obtaining connection fwith the trunk lines while they'are in use.

-When llthe substation callin device isoperated for thel fourthy digiti ,the'repeater repeats two "impulses through therline relay-123 of the .connector H. Each ltinie the relay 123 denergizesv in responseto these impulses, a circuit'is .closed from ground G1 through' the spring 1 36 andits back contact, spring 137 and itsfront contact, vertical magnet'54, side switch wipervv 138 and the -relay 139 tothe battery Alead 115.l The vertical magnet operates'in re sponse to these impulses to raise the switch .v

wipers 51, 52 and 53 tw steps, while the slow acting relay 139 operates to close the circuit of the privatemagnet 56 and maintain it closedl as long as the vertical magnet is operating. After the last impulse is delivered to the vertical magnet, the relay 139 dencrgizes and breaks the circuit of the private magnet 56, which thereupon permits the side"V switch to pass to second position. When the substation calling device is operated for the last digit 0, the connector line relay is denergized ten times, each time completing a circuit from ground G1 through the spring 136 and its back conl tact, spring 137 and its front contact,v rotary magnet 55, springs 140, side switch wiper 138 and relay 139 to the battery lead. The rotary magnet voperates to rotate f the shaft wipers ten` steps onto the contact of the desired line, while the relay 139 operates in the same manner as for the previous digit Y to cause the private magnet to release? the.v

side switch one more step after the last'-; in1`- pulse is delivered. The movement of the Yside switch wipers 141 and 142 from second to third position nally completes the connection between the calling and the called lines.

third position, extends a guarding potenof the called line and closes an energizing switch C'. This guarding potential and circuit extend from ground G11 through the side switch wiper 143, springs 145 and 146, private wiper 53, connector private bank contacts and through the winding 144 tothe battery lead 115. The winding 144 attracts the cut-oil;l armature 147, which disconnects 4circuit for the cut-oE winding 144 of the the switch 'C' from the called line and closes 4 the normally open-contact 148 in the talking circuit. The side switch wiper 138 of the connector, upon reaching third position', comi pletes the circuit of the ringing relay 57,

.y tently so as not to ring'the called subscribercontinuously. When the subscriber at the 4said circuit extendipgyfrom ground TG1" vthrough the interrupter 149, springs 150, relay 57,.side switch wiper 138 andrelay.

the called subscriber. Since the circuit of the ringing relay 57 includes the interrupter 149, said relay. is energized only'intermitcalled substation removes his, receiver, 4or as soon thereafter as thevringmg relay jden.

'y vthe time, .thecfalled substation is provided with talking current" over a circuit extendergizes,- if it-happens to f be energized at ing-v from ground. yG11 at the connector,

through the side switch .wiper 143, @lowerwinding ofi/the connector -back-'bridgerelayv 151,- ringing relay springs `152 and 153,:'side switchwiper1142,shaft wiper 52, line 154,

thence throughv the 'talking'.circuit-.of the substation andback over -the line 155,

through zthe contact 14.8, wiper 51, side l.switch wiper 141, springs 156 and 157 and the upper windingof the relay 151lto battery. The relay- 151, upon (energizing, breaks 57 at the springs 150, and the calling an called subthe circuit of4 the .ringing rela scribers. may now carry on an. uninterrupted conversation over the talking circuit outlined ,byv heavy conductors in the drawings.

' After the conversation is completed, ally the automatic I apparatus employed in.l the connection is released by `the hanging up of the receiver cat .they calling substation.' The hanging up -of the receiver at the substation r1-.destroys the4 energizing circuit of the linefrelay 91 of therepeater' ,The relay 91, upon denergizing, `opens the bridge.-

across the. trunkconductors 49 and 50 `at the springs 110, and also opens thecircuit of the relay `94. n The relay 94, upon def.`

energizing, destroys the holding`-circuit.- off the relay 46 of thev selector E and ofthe holding winding 15 of the line switch C.

The winding 15,-upon denergizing, permits the plunger of the line 'switch to be restored to normal position, while the relay 46, upon denergizing,` completesthe circuit of the fr ground G5' through thespring 85-and its back contact, spring 86 .and its back contact, springs 159, off normal 4springs 44jand magnet .43` to lthe battery lead-70. The magnet 43, upon ...energizingimmediately re-g` stores the selector to normal position, and

\ as soon as the shaft reaches its lowest position,the circuit of the magnet), 43 is` broken at the springs 44.

frivhea the brid'gacrtssfthfitrunk @ia- 5o.

is broken atstherepeater tliedfconnector. linerelay 123"denerg1z'es. ".Thefjrelay 123,"

y and of. the Iprivate from the guarded, privatefbank contact to. re Ozge .magnet 43'. Thisycircult extends private magnet wiper.' 141,' springs '156 .and

relay 124.,l The relay. 124, upomdenergizmg, closes the circuit of the `rel 160 and' breaks the holdingthep'.:

E', respectively. The circuit of-the release :magnete 160 extends. from ground-' "G1" through `the spring 136 and its back-contact, spring 137 and its back contact,mag net 160 and of-normal-1springs 161 tothe lbattery. lead 115. -The magnet 160', upon relays 125 and `1-26 of the selectors E2 zand energizing, .releases the connector and the release circuit is broken at the. springs 161 as soon as the switch shaft reaches itslowest -r position.' The selectors E2 and E arey `re If said line had been busy there vWould'have been a guarding potential at fits connector y private bank contacts, andthe connector 1H would have been prevented from'completing connection therewith in the following'manner: When the private wiper' 53 engagesH a grounded cotact ofa .busy linel,"a.conn'ec tion'is exten ed from saidgroundedcontact th-rough saidwiper, springs 146 'and '145, lower `Winding of the relay151,springs`152 and 153,-.side 'Switch wiper 142` (whichis `then Ain second position), contact 164'tothecalled by the subscriber .at substantion A; a.

spring of the private magnet-relay 139.y

When the private magnet relay-"139 denei-"s'- gizes after-the 'last digit is'called, the spring .l

166,` since it'engages the spring 165'before". 1t 1s. disengaged from thev spng-167,-ifcoxnj.

pletes a circuit fromthe groundedprivate bank contact ofthe busyf line through-*the `private magnet 56 `inseries with thet lower .winding ofgthe relay 151without` allowingA private-magnet to denergize. vThe rel--l the lay 39 beingdenergized and the relays556 y upon energizlng. shifts the holdmg curren magnet and the: relay 151 andfl68, springs 169, relay 170and sp gs,

151 beingenergized, a circuit ,is closed ground G13 through the springs 145 fand 172,1'

thereby. formino Va locking circuit for the'j dependent of the {privat/e l bank contacts. Since :the private` magnet does not have a chance to denergize rafter,...r.

the last digit is called, the side switch re- `mains locked inf second position, "therebyl preventing completion of connection with` the called line through the wipers 141`and 4142, and at thesame time @he busy signal. ing machineM.. 1sy connected with the call'` line through. thek springs-175`'sidefs` 157fj`a1i denser 58.-" www re-.eend

ployed..

position 1 upon .the hanging-,up ofthey receiver at the .calling substation in essentially the Vsame-manner as` when an idle line is called." a

While j I have lillustrated my invention in connection-with a complete automatic .private ybranch exchange system, it is to. be

understood v'that Idonot Wish to limit myself to. such a system,l as the various features of my invention-may be employed in any system in 'Wh-ich. automatic switches are em What I .claim as my .invention is :--v 1. In-y a telephone system, a plurality of subscribersflines, a 'trunk line, meanslincluding' anautomatic switch for extending4 al Iconnection:` from any' one 'of said subscribers lines to-seize'said trunk line, means onVcertainy of said subscribers lines for extending a connectionv over said vtrunk line, andhtmean'sfi for preventing other .of said subscribers vvfrom'- extending such a connec-l tion.

2; a'telephone system, a plurality of subscribers?"lines, al trunkr line .accessible in common'to said subscribers lines, an automatic switch individual to each subscribers line, #a relay associated. with'v said trunk, means includingV said individual .switch for extending a connection 'toward said trunk, meanscontrolledby .said relay for completing a connection from a subscribers line to said trunk, andy means wherebysaid relay may be energized to complete such a connection from `v certain of ,said subscribers lines andeannot be energized fromv others..

3. vI-ny a `telephone system, a' plurality of subscribers lines,an automatic switchindividual-'to each of said lines, an operating magnet for'eachof said switches, a shunt about a Winding of certain of said magnets, a trunk line,7means. including said individual vswitches :for extending the connection from" 1 5. In a telephone` system, a plurality of subscribers lines, a switchv including an operating magnet individual to each of said subscribers lines, a trunk line,means including -i one` of. said switchesk forl extending a connection from asubscribers line to sald A trunk,vv a relay for controlling the circuit of said trunk, an energizing circuitfor said relay including a winding of said operating magnet, and means for varying the resistance of said circuit, depending upon the individual switch with which said trunk is connected.

6. In a telephone system, a plurality of subscribers stations, atrunk line, a repeater abcessiblefrom said subscribers stations' for repeating impulses over said trunk', a relay 'in said repeater, and means whereby -said relay may be energized from certain of said subscribers stationsbut cannot be energized from others.

7S In a telephone system, a plurality of subscribers lines, a trunk line, means including an automatic switch for extendingv a connection from said subscribers lines to -said trunk, a repeater included in said trunk .for repeating impulses over the same, arelay in said repeater for controlling the cir-v cuit of .-saidtrunk, and means whereby said relay maybe energized'to control said. circuit from certain of saidl subscribesi lines but cannot be-so energized from others.

. 8. .-Inxa telephone system, a plurality of subscribers lines, van automatic switchindividual to said lines, lan operating magnet for each of said switches, a trunk line, means including one of said switches for extending va connection from a subscribers line to 'said trunk line, a repeater in said trunk for" re` peating impulses over the' same, a relay in said repeater for controlling the circuit of said trunk, and means for energizing said relay in series with a winding ofthe operating magnet of thel individual switch employed in establishing a connection.

9. In a' telephone system, a plurality of subscribers lines, a non-numerical trunking switch individual to said lines, an operating magnet for each of said switches, a shunt for a winding of certain of saidoperating magnets, a trunk line,means for extending a connection from said individual switches to said trunk line, a repeater in said trunk for repeating impulses over the same, a relay in said repeater for controlling the circuit 1 of said trunk, and a circuit for saidrelay including the loperating magnet of the nonnumerical switch employedv in establishing a connection, said relay being adapted to be energized to control said circuit when it is connected in series with an operating magnet having" a shunt, and saidv relay being 120 adapted not to be so energized when itis lso connected in vseries with an operating magv net which does not havel a shunt.

l0. In a telephone system, 'a plurality of subscribers lines, means for establishing va plurality of dierent kinds of connections from said lines, means whereby certain ofA said subscribers are prevented fromv establishing certain' ofv said connections, and

neansfor giving a signal when a subscriber connection from whichl attempts to make a heis barred.

1l, In a telephone system, a plurality of*4 subscribers lines, a trunk line accessible 'in common to said subscribers lines, 'means on said subscribers. lines for extendinga connectlon to saidy trunkline, means whereby i certain of saidlsubscribers are prevented from establishing a connection over, said "12. In a telephone system', a plurality` of subscribers"lines, a trunk line accessible in means for giving afslgnal when one of saidv yid alto each. of said lines, an operating common to said lines, means wherebyv certain'of said, subscribers can transmlt impulses fever-.said trunk ltoestablish a ,coniiection'v with-,a second subscribers line,

.means -forpreveilting other of said subscribers rfromes'tablishingsuch a connection, and

last-mentionedlsubscribers' attempts to establish a connectionover said trunk, 13. In atelephone system, a plurality of subscribers lines, a trunk. line, means includlng an automatic switch fon extending a connection from any one of said, subscribers lines to said trunk line, means on certain of said subscribers lines for extending a connection over said trunk line, .means for preventing other' of vsaid subscribers from extending vsuch a connection, and means for Y giving a signal when one of saidvlastmentioned subscribers attempts to extend such a connection.

11i. In a telephone system, a pluralitybf subscribers lines, a trunk line accessible in common to Asaid subscribers lmes, an automatic switch individual to each subscribers V ,l y l, 4switch including arotary magnet,

line, a relay associated with,y said trunk, means including said individual switch for extendingnaeonnection toward said trunk, means. controlled by said relay for completing a connection from a subscribers line to said trunk,".lmeans whereby said. relay may,

be energized to Ycomplete such a connection from certainof said subscribers lines and cannot be.. so energized from others, and, g1 means for giving 'a signal when a subscriber attempts toextend a connection over said trunk and said relay is not so'energized. Y

1b. Ina telephone` system, a plurality of subscribers lines, an automatic switch indl# V'"'ineignet?"for each of, said switches, a shunt about'. a'winding of certain of said magnets,v

a trunk line,'means including said individi I said rotary magnet, ay switch',laprivt e'fj' 'magnet for controllingfmsa'd by said rotary magnet;l

rupter relay for controlling'.thjtm In a telephone sy tem,

subscribers lines, a nodi-numerical n `switch individual to said 1319i all operating;A

magnet for each ofsaid" v vitches,"ha shun r' `a winding of certain of', nets, a trunk line, means forf extending from said in vidua:fswitchesftoso ssa operating-mtg;

connection said trunk line, a repeax ,u repeatingl impulses ovegr Athe x y in said repeater for controlling' the clrcuit of. said trunk, a circuit for` sald relay Sini".

cluding the operatingrjxvnagnet nfnrthe'fnon- 95' numerical switch employed inestab'linshing a connection, means wheijeby said relay is fenergized when it is coniifected in' series with' an operating magnet i1` ving a shuiit whereby said relay is not energized 'when tf 5100 kis connected in ser1es with an operatiiigma-g-- net which doesnot have shii'nt, and mfean for giving a signal w ena subscriber"at tempts to extend a ciinectionbver "said-V trunk when said relaymifsdenergizhed 18. In a telephone system,fan"faito1`n fti rupter relay for contrllingfthe"circuit frr venting saidl interrupter- Y ing until after the priva 1931.11l a ftelephone fari-a oma switch including a rotary magnet, @an Vvint sald rotary magnet,`a private inagn'ety'a l cuit for said magnet controlled.,by/saidroflz tary magnet, a normally openjcircuit said interrupteur relay including Contact springs controlled by. rivateinagnet, whereby said interruptor re ay is"y prevented y from operating until after said privatemag-Ql25- net has operated. I fn v 20- In a telephone Sistem', aniutomtm switch including-fa* rotary magnet, a'11;iiite"r.

relayf'for controlling the' circuit-j-for said i'etaiy magnet, a vsefcondjnmagne't,'v 'a cir?V 130 cuit for said second magnet controlled by said rotary magnet, and means forpreventing 'said' relay from energizing until after the second'magnet has energized.

21.]"In a'telephone system, a magnet, a

-circuit controlling relay: and an auxihary relay, means'whereb the circuit controlling relay controls. the circuit of said ma et, a circuit for said auxiliary relay'contro led by said rotary magnet, and a normally open switch point hin the circuit of said circuit means controlled Aby said circuit contro ling relay for controlling the circuit of said ro-- tary magnet, 'and means controlled by said auxiliary relay for controllin the circuit vof said circuit controlling re a whereby said circuit controlling relay cannot be energized until after the auxiliary relay is enerze Y 23. In a telegione system, a plurality of lines, a trunkl e, .trunkin equipment for connecting any one of sai lines with the trunk, said vtrunk normally inoperative for extendin a connection therethrough, means for ren `erin'g Asaid trunk operative, said..

trunking equipment comprising a bridgel cutoi relay for renderin the equipment individual to the calling 'ne inoperative when the calling line is called, said means comprising a relay individual to the trunk, and

an energizingcircuit 'for said relay comprising the said bridge cut-ofi' relay.

24. n a tele lione system, a plurality of lines, a trunk e, trunkin equipment for 1 connecting any one'of sai lines with the l relay. A, y

25. In a telephone system, a line, a second A operative to extend`v a connection, thercj olf relayV for renderingi, t

trunk, saidytrunknormally inoperative for extendin a connection therethrough, means for ren erin said .trunk operative, said trunking equipment com rising abridge cute equipment individual to the calling ne inoperativewhen the callinglinev is called, said means `comprisingra relay individual `,to the trunk, an

energizing circuit for said relay compris-.. ing the said bridge cut-0E relay, and a circuit vin multiple with said bridge cut-oli:`

line, a group of lines, atrunk line,'trunk ing vequipment for connecting either the first or second 'line with any one of the lines of said group, orl for connectingone at a. time either the first or'secondline-with th'esaid4 trunk line,'saidA trunk normally in,-

through, means for automatically renderingl said trunk operative when connected with the first line, said means inoperative yfor lrendering the trunk operativewhenever thev trunk is connected with the second line.

26. Ina telephone system, a line, `a second line, a grou 4of lines, a trunk line, .trunking equipment or connecting either the first orA second line with any one of the lines of ,said grou or for connecting one at a time either the rst or second line with the said' trunk" fline, said trunk normally inoperative to extend a connection. therethrough, means for automatically rendering said trunk opera.

tive when connected with the first line, said means inoperative for rendering the trunk operative whenever the trunk lis connected 'with thesecond line, and means for signaling the second line that the trunk isinoperative. t 4

27. In a telephone system,.a line, a second line', a group of lines, na trunk line, trunking equipment for connecting eithe'i'the first or second line with any one of the lines of said grou ,or forg connecting, one at a time either the rst or second line with the said trunk line, said trunk 'normally inoperative to ex-I f tend a connection therethrough, means vfor automatically rendering said trunk operative when connected with the first line, said means inoperative for rendering the trunk operative whenever the trunk is connected with the second line, and means for signal-` ing the second line that the trunk is inop-v erative, said trunk line.

28. In a telephone system, a line, a'secondy last means individual to the line, a group of lines, atrunk line, trunking equipment for connecting either the iirst or second line with any one of the linesof said group, or for connecting one' at a time either the rst or second line-with the said trunk 'ica line, said trunk normally operative to extend a connection therethrough, means for auto' matically rendering said trunk operative v means inoperative for rendering the trunk f when connected with the first line, said operative whenever the trunk is connected' with 'the second'line, a signal and means in`- divi'dual to the trunk Ifor signaling the sec- ,ond line that the trunk isinoperativa 29. In a telephone system', aline, a second line, a group of lines, a trunk line, trunking equipment for connecting either the first or second line with any one of the lines of saidv v grou or for connecting one at a time either thel rst or second line with said trunk-line, said trunk normally inoperative to extend la` v connection therethrough, means for auto-v matically rendering saidv trunk operative* when connected with the-"first line, said' means inoperative for rendering the trunk 'operative whenever the trunk isconnected'l with the second line, and means for signal'- Lacasseing the` secondi li`r1e thatthe trunky is inoperat'ive, thesignal alyvays inaccessible to the .y 3 0. `In atelephone sys-tem, a line( line, a grou om lines, a trunk lineft line, said trunk normally inoperative to extenda connection therethrough, means for automatically rendering said. trunk opera f tive -whenpconnect'ed with the iirst line,I said 'means inoperative for renderin the trunk operative Wheneverv thel trunk y1s connected with the second line, and means for signaling the second line that t-he trunk is inoperative,

the line.

' m31.: In a telephone system, a line, a second line, a grou of lines, a trunk line, trunking equipment v 4or connecting either the first or second line with any one of the lines of said group, or for connecting one at a time `either the lirst or second line with thesaid'trunk line, said trunk normally operative to extend a ,connection therethrough, means for automatically renderin .said trunk operative when connected with the iirst line, said means inoperative for rendering the' trunk operative whenever the trunk is connected with the second line, a signal and means individual to the trunk for signaling the second line that the trunk is inoperative, said signal always inaccessible to the first line.

x32. Ina telephone system, a line, a second line, a group of lines, a trunk line, trunking equipment for connecting either the rst or second line with any one ofthe lines of said group, or for connecting one at a time either the Erst or second line with said trunk line, said trunk normally inoperative to extend a connection therethrough, a relay individual to said trunk for rendering the trunk operative, an energizing 'circuit for said relay having a branch individual to the first line and a branch individual to the second line, means in the branch individual to thesecond line for preventing the elay1 from energizing for the purpose set 33. In a telephone system, a line, a second line, a group of lines, a trunk line, trunking equipment for connecting either the rst or second line With any one of the lines of said group,` or for connecting one at a time either Vthe first or second line with said trunk line, said trunk normally inoperative to extend a connection therethrough, a relay individual to said trunk lfor rendering the trunk inoperative, an energizing circuit for said relay having a branch individual to ,the first line and a branch individuall to the second line, and means in the branch either the first or second signal always.y inaccessible rto lthe lirst y insuring the supply offsufl'ci line, a group of lines,

rseparate from the talking conductor.

. lease mechanism controlled over said enervidual tothe first line. f ply of vsuicient curren lay to render the trunk 34, In a telephone sy line, agroup of lines,`v` ,L ing' equipment for connec or ',second line WithA anyjg'c said lgroup, or for connec line, said trunk normally tend a connection ther dividual to saidy f trun m trunk operative, v an ene said relay having af-b thefrstline and a bran, second line, means int to the second Aline for pr 4from energizing for thf" and means individual n energize the relay to rende erativewmh l,

35. In a telephonemsysteni ing equipment for connctin weith lie or` second line `with anyaforieml h] `said group, or for connectin t either the first or second line with sai line, said trunk normally inoperativevto ex,- tend a connection therethrough, a relay individual to said trunk for rendering the trunk operative, an energizing circuit for said relay having a branch individual to the first line and a branch individual to the second line, means in the branch individual to the. second line for preventing the relay from energizing for the purpose setforth, said energizing circuit extending from the calling line to the trunk over a conductor 36. In a telephone system, a line, a second l line, a grou of lines, a trunk line, trunking equipment or connecting either the Iirst or second line with any one of the lines of said group, or for connecting one at a time either the first or second line with said trunk line," said trunk normally inoperative to-eXtend a connection therethrough, a relay individual to said trunk for rendering the trunk operative, an energizing circult for said relay having a branch individual to the rst line and a branch individual to the second line, means in the branch individual to the second line for preventing the relay from energizing for the purpose set forth, said energizing circuit extending from the calling line to the trunk over a conductor separate from the talking conductor, and release. mechanism for the trunkng equipment, said regizing circuit.

37. In a telephone system, a line, a second-V 1ine,' a group of lines, a trunk line, trunking` equipment or connecting either the first or second line with any one of the lines of said group, or for connecting one at a time either 'the rst or second -line with said trunk line,

said trunk normallyinoperative to extend a connection therethrough, a relay individual to said trunk for rendering theltrunk operative, any energizing circult for said relay having. a branch individual to the Iirst "line and a branch individual to the second line,

' means in the branch individual to the second line for preventing'the rela `from enerf gizing'for the purpose set fort said ener- 'zing circuit extending from the calling .l1ne tothe trunk over aconductor separate from the talking conductor, release mechanism for thetrunking equipment, said release mechanism controlled over said energizing circuit, and means for making the.

' trunk busywhena connection is extended to the same, said means comprising said energizin circuit.

38.- n a telephone system, subscribers lines of twoekinds, means 'responsive 'to a calling line ofi-either kind for performing a preliminary automatic. trunking operation,I and means actuated only when the calling -v line is of a particular kind'to perform a second automatic trunking operation.

39. In a telephone system, subscribers lines of twov kinds, meansincluding trunk lines for connecting callin and called lines,

means responsive to a ca mg line of either kind for automatically connecting-such calling line with an idle trunk line, other ltrunk lines, and means actuated onl one of said ot er trunk lines.

40. In a telephone system, ailurality ofw.

subscribers lines, meansinclu lng a' plurality of automatic switches for establishingwhen the.. calling line is of a particular kind for further extendin such calling line to'an. .idle-f a plurality of di'erent kindsof connections from said lines, means whereby certain of said subscribers -are prevented from establishing certain 'of said connections, vand means for givin a signal when a subscriber attempts to ma e a connection from which 

